The molecular mechanism of switching from adult to fetal hemoglobin is not completely understood. A variety of chemical agents have been tried, both in vivo and in vitro, to increase fetal hemoglobin (Hb F) synthesis in adult cell systems. Several different mechanisms have been proposed. However, there appears to be no unified mechanism underlying the actions of these diverse agents. The rat has no distinct fetal hemoglobin like the humans but does have significant variation in hemoglobin proportions between newborn and adult blood, indicating some similarities between the two species with regard to certain aspects of beta-chain switching. It has been shown consistently that concurrent prostaglandin synthesis is required to stimulate newborn-like hemoglobin synthesis in adult rats but not for hemoglobin synthesis per se. However, analogous requirement of concurrent prostaglandin synthesis in human Hb F synthesis has not been examined. This proposal is designed to test the hypothesis that concurrent prostaglandin synthesis is required to stimulate Hb F in normal adult humans and sickle cell patients and to elucidate the molecular basis for such requirement using the following approaches. 1. Culture of blood BFU-E (burst forming unit-erythroid) derived colonies will be employed to assess the effects of 5-azacytidine, hydroxyurea, butyrate and acetate on Hb F synthesis in the presence and absence of locally produced concurrent prostaglandin synthesis. Hemoglobin components will be measured either by ion-exchange chromatography or by HPLC. 2. The production of alpha, beta, and gamma globin chains the proportions of the globin mRNA that are produced within the erythroid colonies will be measured. 3. The possibility that concurrent prostaglandin synthesis is required as a signaling process to activate gamma-gene expression in adult erythroid cells will be examined. The results of this study should contribute to a better understanding of the mechanism of stimulation of Hb F synthesis beyond the neonatal stage. Knowledge of the control mechanism regulating Hb F synthesis in adult life should help in designing treatments for diseases like sickle cell anemia and beta-thalassemia.